How to set a principal point for a camera
I'm not entirely sure what you're looking for, but it sounds like the lens's Shift properties.


Here's the default settings:


And here's the same camera with an X-axis shift of 0.2:


Note that this is not the same as simply rotating the camera - adjusting the Shift doesn't change the perspective. You can think of it as if you had a larger image and you cropped a side of it off.